Name: Hydrochloric Acid
CAS No: Hydrochloric acid [7647-01-0]
BP: Hydrochloric Acid JP: Hydrochloric Acid PhEur: Hydrochloric Acid, Concentrated USP-NF: Hydrochloric Acid
Acidum hydrochloridum concentratum; chlorohydric acid; concentrated hydrochloric acid; E507.
Hydrochloric acid [7647-01-0]
HCl 36.46
Hydrochloric acid is widely used as an acidifying agent, in a variety of pharmaceutical and food preparations (see Section 16). It may also be used to prepare dilute hydrochloric acid, which in addition to its use as an excipient has some therapeutic use, intravenously in the management of metabolic alkalosis, and orally for the treatment of achlorhydria. See Section 17.
Hydrochloric acid occurs as a clear, colorless, fuming aqueous solution of hydrogen chloride, with a pungent odor. The JP XV specifies that hydrochloric acid contains 35.0–38.0% w/w of HCl; the PhEur 6.0 specifies that hydrochloric acid contains 35.0–39.0% w/w of HCl; and the USP32–NF27 specifies that hydrochloric acid contains 36.5–38.0% w/w of HCl. See also Section 9.
See Table I.
Acidity/alkalinity pH = 0.1 (10% v/v aqueous solution) Boiling point 1108C (constant boiling mixture of 20.24% w/w HCl) Density 1.18 g/cm3 at 208C Freezing point 248C Refractive index n D 20 = 1.342 (10% v/v aqueous solution) Solubility Miscible with water; soluble in diethyl ether, ethanol (95%), and methanol.
Hydrochloric acid should be stored in a well-closed, glass or other inert container at a temperature below 308C. Storage in close proximity to concentrated alkalis, metals, and cyanides should be avoided.
Hydrochloric acid reacts violently with alkalis, with the evolution of a large amount of heat. Hydrochloric acid also reacts with many metals, liberating hydrogen.
Hydrochloric acid is an aqueous solution of hydrogen chloride gas produced by a number of methods including: the reaction of sodium chloride and sulfuric acid; the constituent elements; as a by-product from the electrolysis of sodium hydroxide; and as a by-product during the chlorination of hydrocarbons.
When used diluted, at low concentration, hydrochloric acid is not usually associated with any adverse effects. However, the concentrated solution is corrosive and can cause severe damage on contact with the eyes and skin, or if ingested. LD50 (mouse, IP): 1.4 g/kg(1) LD50 (rabbit, oral): 0.9 g/kg
Caution should be exercised when handling hydrochloric acid, and suitable protection against inhalation and spillage should be taken. Eye protection, gloves, face mask, apron, and respirator are recommended, depending on the circumstances and quantity of hydrochloric acid handled. Spillages should be diluted with copious amounts of water and run to waste. Splashes on the skin and eyes should be treated by immediate and prolonged washing with large amounts of water and medical attention should be sought. Fumes can cause irritation to the eyes, nose, and respiratory system; prolonged exposure to fumes may damage the lungs. In the UK, the recommended short-term workplace exposure limit for hydrogen chloride gas and aerosol mists is 8 mg/m3 (5 ppm). The long-term exposure limit (8-hour TWA) is 2 mg/m3 (1 ppm).(2)
GRAS listed. Accepted for use as a food additive in Europe. Included in the FDA Inactive Ingredients Database (dental solutions; epidural injections; IM, IV, and SC injections; inhalations; ophthalmic preparations; oral solutions; nasal, otic, rectal, and topical preparations). Included in parenteral and nonparenteral medicines licensed in the UK. Included in the Canadian List of Acceptable Non-medicinal Ingredients.
Dilute hydrochloric acid. Dilute hydrochloric acid Synonyms Acidum hydrochloridum dilutum; diluted hydrochloric acid. Density 1.05 g/cm3 at 208C Comments The JP XV and PhEur 6.0 specify that dilute hydrochloric acid contains 9.5–10.5% w/w of HCl and is prepared by mixing 274 g of hydrochloric acid with 726 g of water. The USP32–NF27 specifies 9.5–10.5% w/v of HCl, prepared by mixing 226mL of hydrochloric acid with sufficient water to make 1000 mL.
In pharmaceutical formulations, dilute hydrochloric acid is usually used as an acidifying agent in preference to hydrochloric acid. Hydrochloric acid is also used therapeutically as an escharotic.(3) The PhEur 6.0 also contains a specification for hydrochloric acid, dilute; see Section 17. A specification for hydrochloric acid is contained in the Food Chemicals Codex (FCC).(4) The EINECS number for hydrochloric acid is 231-595-7. The PubChem Compound ID (CID) for hydrochloric acid is 313.